1. Field of the Invention
The present invention generally relates to an adapter card supporting Peripheral Component Interconnect (PCI) Express bus interface, and more particularly to an apparatus and method for providing an alternative power source to a graphics card.
2. Description of the Related Art
Unless otherwise indicated herein, the approaches described in this first portion are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A computer system typically includes a dedicated graphics subsystem, such as a graphics card, to render graphics images for the computer system. Peripheral Component Interconnect Express (PCI-E) has been adopted by the industry as the standard bus interface for connecting the graphics card and the motherboard of the computer system.
A typical graphics card 100 includes at least a processing unit, memory unit, and traces on a printed circuit board (PCB). The PCB generally includes multiple layers with the traces (not shown) running through at least the top and bottom layers. The traces are made of connecting materials and are connected to the various components to facilitate signal transmission and power supply. The traces are also connected to gold-plated terminals of a card-edge connector (also referred to as “gold fingers.”) To illustrate, FIG. 1A is a simplified schematic diagram showing the conventional graphics card 100 with the PCI-E interface and with a set of gold fingers 110. The gold fingers 110 are divided into a first portion 102 and a second portion 104. Here, the gold fingers in the first portion 102 are primarily responsible for carrying data signals, and the gold fingers in the second portion 104 are primarily responsible for supplying power to the entire graphics card 100. Generally, the graphics card 100 is powered up by connecting a power supply to a dummy pad (not shown). In particular, the dummy pad is connected to the second portion 104 through a wire, so that the electric charges from the power supply flow through the second portion 104. The electric charges are then directed to the first portion 102 from the second portion 104.
One existing solution is to connect the first portion 102 to the second portion 104 using a wire. FIG. 1B is a schematic diagram showing the structure of a conventional gold finger layout and wire connections. Here, each of the first portion 102 and the second portion 104 includes shortened gold fingers 118 and 120, respectively. For the first portion 102, the shortened gold finger 118 resides on a top layer 112 of a PCB. For the second portion 104, the shortened gold finger 120 resides on a bottom layer 116 of the same PCB. The shortened gold fingers serve two purposes. One is to provide a fool-proof design, which ensures the proper insertion of the graphics card into a slot, so that connection is secured. The other is to supply power to the graphics card. Both of the shortened gold fingers 118 and 120 are connected to through holes 124 and 126, respectively. The through holes 124 and 126 are cylindrically shaped and with electroplated medium, which is capable of transmitting electrical signals such as power signals. An external power source is connected to a dummy pad 130, which is connected to the shortened gold finger 120 from the second portion 104 on the bottom layer 116. To relay power signal from the second portion 104 to the first portion 102, a wire 128 is used. The wire 128 connects the shortened gold finger 118 of the first portion 102 to the shortened gold finger 120 of the second portion 104. The wire 128 is positioned in a middle layer 114 of the PCB. As shown in FIG. 1B, the wire 128 is connected to the shortened gold finger 120 on the bottom layer 116 via the through hole 126 and is also connected to the shortened gold finger 118 on the top layer 112 via the through hole 124. Positioning the wire 128 in a different layer, as opposed to either on the top layer 112 or the bottom layer 116, helps to reduce signal interferences caused by running the wire 128 across the PCB. However, the problem of signal interferences still can not be removed completely, especially if the strength of the signal traveling on the wire 128 is increased. With signal interferences, the overall quality of the signal transmission, especially at high speed, still suffers.
FIG. 1C is a schematic diagram showing the structure of another conventional gold finger layout and wire connections. Here, a wire 160 is positioned on a top layer 150 of a PCB. A shortened gold finger 154 is positioned on one end of a set of gold fingers 152, which are also positioned on the same top layer 150. The wire 160 is connected from the shortened gold finger 154 on the top layer 150 to a dummy pad 158. The dummy pad 158 generally is positioned close to the location of the shortened gold finger 154 and as discussed above, is often connected to a power supply. In between the shortened gold finger 154 and the dummy pad 158 is a last gold finger 156.
The illustrated configuration has a notable shortcoming. Since the wire 160 is positioned on the top layer 150, a trace 162 connecting to the last gold finger 156, which is also positioned on the same top layer 150, necessarily intersects with the wire 160 connecting between the shortened gold finger 154 and the dummy pad 158. Such an intersection creates an impermissible short circuit. To avoid the short circuit, the last gold finger 156 is in effect rendered useless (i.e., cannot be connected to a trace) but still occupies precious space on the PCB.
As the foregoing illustrates, what is needed is a method and apparatus capable of providing an alternative power source while maintaining the current gold finger layout, and address at least the problems set forth above.